Light-developable direct-print silver halide emulsions containing urazole compounds as halogen acceptors



United States Patent 01 hce 3,396,017 Patented Aug. 6, 1968 3,396,017 LIGHT-DEVELOPABLE DIRECT-PRINT SILVER HALIDE EMULSIONS CONTAINING URAZOLE COMPOUNDS AS HALOGEN ACCEPTORS Robert E. Bacon and Bernard D. Illingsworth, Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Oct. 23, 1964, Ser. No. 406,186 18 Claims. (Cl. 96-27) ABSTRACT OF THE DISCLOSURE Direct-print emulsions comprising urazole halogen acceptors of the following formula:

wherein (1) X and Z are each selected from the group consisting of an oxygen atom, a sulfur atom, a selenium atom and an imino radical; and

(2) R R and R are each selected from the group consisting of a hydrogen atom, an alkyl radical, an aryl radical and an amino radical, except that at least one of R and R is a hydrogen atom.

The present invention relates to photography, and more particularly, to light-developable or direct-print photographic silver halide emulsions.

Radiation-sensitive papers adapted for light recording, e.g., oscillographic recording, are known. Typical of such papers are the developing-out and print-out type. The dcveloping-out type, as the name implies, requires that the exposed material be chemically developed, fixed and washed in order to provide .a stable visible image on said material. The print-out type of material develops on exposure and requires no development step. The print-out type is generally much slower than the developing-out type and the images are unstable and have a short life.

A third type of radiation-sensitive material especially suitable for light-writin g and oscillographic recording com prises a hydrophilic colloid-silver halide emulsion layer which, when exposed to a high intensity source of electromagnetic radiation, forms a latent image which can then be developed by subsequent general exposure to a second source of radiation of lower intensity. Such direct-writing or direct-print emulsions are faster than print-out emulsions and require no chemical development. However, many of the recording papers of this third type have a slow rate of photodevelopment and the background areas tend to build up to obscure the image on subsequent exposure to light.

It is an object of this invention to provide a new class of light-developable, direct-print, radiation-sensitive silver halide emulsions.

It is another object of this invention to provide novel photographic silver halide emulsions suitable for preparing direct-print recording paper having a high rate of photodevelopment.

It is another object of this invention to provide novel photographic light-developablc, direct-print silver halide emulsions that can be chemically developed and fixed before or after photodevel-oprnent to make archival-quality records.

It is another object of this invention to provide new photodevelopable photographic silver halide emulsions that are characterized as having high density ditferential between the initially-exposed and unexposed area upon photo-deve-lopment.

It is also an object of this invention to provide new light-developable photographic silver halide emulsions that have high resistance in the initially-unexposed areas to density increase upon photodevelopment and subsequent exposure to light.

It is likewise an object of this invention to provide a new process for forming images by light-development.

These and other objects of the invention are accomplished by incorporating into light-developable, directprint, radiation-sensitive silver halide emulsions a urazole halogen acceptor.

A wide variety of urazoles can be utilized in the lightdevelopable, direct-print photographic silver halide emulsions of the invention as halogen acceptors. Typical of the feature urazole addenda of the invention can be rep resented by the formula wherein: X and Z can each be an oxygen atom, a sulfur atom, a selenium atom, or an imino radical (=NH); and R R3 and R can each bea hydrogen atom, an aryl radical such as naplrthyl or phenyl, an amino radical (-NH or an alkyl radical typically having 1 to 20 carbon atoms, :and more generally, 1 to 8 carbon atoms, such as methyl, ethyl, propyl, butyl, amyl, octyl, decyl, dodecyl, octadecyl, eicosyl, etc., except that at least one of R and R is a hydrogen atom. Thiourazoles, that is, compounds wherein at least one of X or Z is a sulfur or oxygen atom are particularly useful halogen acceptors. Also, salts of the urazoles can be utilized. Urazoles, being acidic materials, form organic or inorganic salts with basic materials, such salts being suitably used as addenda in the present emulsions. Typical of such salts are sodium, hydrazine, ammonium and the like.

Illustrative urazoles that can be utilized either alone or in admixture, as halogen acceptors in the silver halide emulsions of the invention include:

urazole 3-thiourazole 3,5-dithiourazole 3,5-dithiourazole hydrazine salt 4-aminourazole hydrazine salt 3,5-dithiour-azole hydrazine salt urazole sodium salt 4-( 1-naphthyl)urazole 4-ethylurazole l-phenylurazole 4-phenylurazole l-butylurazole l-ootyl urazole 4butyl-3,5-dithiourazole 1,4-diphenylurazole 1,4dibutylurazole 1,4-dibutyl-3,S-dithiourazole 1,4-diphenyl-3,S-dithiourazole 1-ethyl-4-phenylurazole l-ethyl-4-phenyl-3,S-dithiourazole 3-thio-5-iminourazole 3,5-diselenourazole The concentration of urazoles utlized in the emulsions of the invention can be widely varied in accordance with usual practice. Generally, about .1 to mole percent,

and preferably about 1 to 50 mole percent, based on the silver halide in the emulsion, of urazole is utilized.

A wide variety of light-developable, direct-print, photographic silver halide emulsions can be utilized in the invention, such being well known to those skilled in the art. Suitable silver halides include silver chloride, silver bromide, silver bromoiodide, silver chloroiodide, and silver chlorobromoiodide. The preferred emulsions are those wherein the silver halide is predominantly bromide. For a description of suitable emulsions, reference is made to Davey et al., U.S. Patent 2,592,250, issued Apr. 8, 1952; Glafkides, Photographic Chemistry, vol. 1, pp. 31-2, Fountain Press, London; and McBride Application, Ser. No. 222,964, filed Sept. 11, 1962, now abandoned, wherein is discolsed the preparation of silver halide emulsions with organic thioether silver halide solvents present during the grain growth of the silver halide. 1n the McBride application is taught the addition of the thioether silver halide solvent to the colloidal material in which the silver halide is precipitated, during the precipitation of the silver halide or to the silver halide prior to or during the ripening of the silver halide. Typical of such thioethers are 3, 6- dithia 1,8-octanediol, 1,10-dithia-4,7,13,16-tetraoxacyclooctadecane, 7,10 diaza-l,16-dicarboxamido-3,14-dithiahexadecane 6,11-dione, and 1,17-di-(N-ethylcarbamyl)- 6,12-dithia-9-oxaheptadecane. The amount of thioether utilized to prepare the silver halide emulsions described in the McBride application can be widely varied although about .1 to 25 g. of thioether per mole of silver halide is generally utilized. The present silver halide emulsions generally have an average grain size of about .1 to 10 microns, and more generally about .5 to 1 micron.

, The so-called internal image emulsions can be used in the invention, such having silver halide grains wherein a predominant amount of the sensitivity is internal to the grains. Such internal image emulsions are those which, when measured according to normal photographic techniques by coating a test portion of the emulsion on a transparent support, exposing to a light intensity scale having a fixed time between 1 10 and 1 second, bleaching minutes in a 0.3% potassium ferricyanide solution at 65 F. and developing for about 5 minutes at 65 F. in Developer B below (an internal-type developer), have a sensitivity, measured at a density of 0.1 above fog, greater than the sensitivity of an identical test portion which has been exposed in the same way and developed for 6 minutes at 68 F. in Developer A below (a sur face-type developer).

DEVELOPER A g. N-methyl-p-aminophenol sulfate 0.31 Sodium sulfite, desiccated 39.6 Hydroquinone 6.0 Sodium carbonate, desiccated 18.7 Potassium bromide 0.86 Citric acid 0.68 Potassium metabisulfite 1.5 Water to make 1 liter.

DEVELOPER B g. Nmethyl-p-aminophenol sulfate 2.0 Sodium sulfite, desiccated 90.0 Hydroquinone 8.0 Sodium carbonate, monohydrate 52.5 Potassium bromide 5.0 Sodium thiosulfate 10.0

Water to make 1 liter.

A wide variety of hydrophilic, water-permeable organic colloids can be suitably utilized in preparing the silver halide emulsions or dispersions of the invention. Gelatin is preferably utilized although other colloidal material such as colloidal albumin, cellulose derivatives, synthetic resins or the like can be utilized. Suitable colloids that can be used are polyvinyl alcohol or a hydrolyzed polyvinyl acetate as described in Lowe, U.S. Patent 2,286,215, issued June 16, 1942; a far hydrolyzed cellulose ester such, as cellulose acetate hydrolyzed to an acetyl content of 19 to 26% as described in U.S. Patent 2,327,808 of Lowe and Clark, issued Aug. 24, 1943; a water-soluble ethanolamine cellulose acetate as described in Yutzy, U.S. Patent 2,322,085, issued June 15, 1943; a polyacrylamide having a combined acrylamide content of 30 to 60% and a specific viscosity of 0.25 to 1.5 or an imidized polyacrylamide of like acrylamide content and viscosity as described in Lowe et al. U.S. Patent 2,541,474, issued Feb. 13, 1951; or the like organic colloids as described in Lowe U.S. Patent 2,563,791, issued Aug. 7, 1951; Unruh et al. U.S. Patent 2,768,154, issued Oct. 23, 1956; Unruh et al. U.S. Patent 2,808,331, issued Oct. 1, 1957; and Illingsworth et al. U.S. Patent 2,852,382, issued Sept. 19, 1958.

Lead ions can be used in the precipitation or formation of the silver halide used in the emulsions of the invention. Water-soluble lead salts are typically added with a watersoluble silver salt to an appropriate water-soluble halide to precipitate a lead-silver halide. The amount of lead used in the present silver halide emulsions typically ranges from about .01 to 5 .mole percent based on the silver.

Although silver halide emulsions are generally made with an equivalent or slight excess of halide ion present, additional water-soluble iodide to the silver halide emulsion after its precipitation but before it is coated can be added. More generally, about .1 to 50 mole percent, and preferably about 1 to 10 mole percent of water-soluble iodide based on the silver halide in the emulsion is used. Illustrative water-soluble iodides include ammonium, calcium, lithium, magnesium, potassium, or sodium iodide.

The subject photodevelopable photographic silver halide emulsions of the invention can contain other conventional halogen acceptors in addition to the feature urazole compounds described above, the addenda generally utilized in such products including gelatin hardeners, gelatin plasticizers, coating aids and the like, as well as spectral sensitizing dyes of the type described in copending Jones Application, U.S. Ser. No. 380,044, filed July 2, 1964, and other spectral sensitizing dyes known in the art.

The above-described emulsions of the invention can be coated on a wide variety of supports in accordance with usual practice. Typical supports for photographic elements of the invention include paper, cellulose nitrate film, cellulose acetate film, polyvinyl acetal film, polystyrene film, polyethyleneterephthalate film and related films of resinous materials and others.

In forming a photodeveloped image with a typical photographic element containing an emulsion of the invention, the photographic element is initially exposed to a relatively short duration and high intensity source of electromagnetic radiation (e.g., at least about .1 foot-candle second at an intensity of more than about 100 footcandles) such as a high intensity light source rich in blue and ultraviolet light such as are used in oscillographs descrbied in Heilan-d, U.S. Patent 2,580,427, issued Jan. 1, 1952, high intensity visible light, X-radiation and the like, to form a latent image in the emulsion of the photographic element, and thereafter the resulting latent image is photodeveloped by overall exposure of the emulsion to a radiation source of lower intensity than the original exposure, such as to a conventional fluorescent light, light from incandescent lamps commonly used for general illumination, or even ordinary daylight. Generally, the latent image formed in the emulsion in the first instance is not visible and does not become visible until photodevelopment. Heat is desirably utilized during the photodevelopment step. Typically the subject emulsions are heated to a temperature of about C. to 200 C. for about 1 to 30 seconds and photodeveloped after the initial high intensity exposure.

If desired, photographic elements containing the emulsions of the invention can be developed and fixed in aqueous chemical developing-out and fixing solutions after the initial exposure forming the latent image, or after the above-described photodeveloprnent, to make archival-quality records.

The invention is further illustrated by the following examples of preferred embodiments thereof.

Example 1 A light-developable, direct-print, large-grain gelatinesilver chlorobrom-ide emulsion (95 mole percent bromide, 5 mole percent chloride) having silver halide grains of high internal sensitivity was prepared by slowly adding an aqueous solution of silver nitrate containing .85 g. of lead nitrate per mole of silver to an agitated aqueous acidic gelatin solution (pH to about 2 with nitric acid) containing a stoichiometric excess of potassium chloride and potassium bromide, .5 g. of a thioether silver halide solvent of the type described in McBride application Ser. No. 222,964, filed Sept. 11, 1962, per mole of silver also being added during the silver halide precipitation. The emulsion was washed with water to remove water-soluble salts. The prepared emulsion was divided up into several portions and to each of such portions of emulsion was added to urazole halogen acceptor as indicated in Table I below. The resulting emulsions were coated on paper supports at a silver coverage of 258 mg. per square foot and at a gelatin coverage of 565 mg. per square foot. Strips of each coating containing various halogen acceptors, and a control strip containing no urazole halogen acceptor, were image-exposed wherein the original image constituted opaque bars with a high intensity xenon lamp (Heiland Strobonar 100 watt-second xenon lamp for about .002 second at a distance of about 8 feet) and photodeveloped for 5 minutes with a 60 foot-candle cool white fluorescent light. Table I below summarizes the densities of the image areas (D the densities of the background areas (D and the density differences between such areas (AD) for each of the coatings. The concentration of halogen acceptor indicated in the table is in mole percent based on the silver halide in the emulsion.

TABLE I Urazole Halogen Acceptor Dmhx Dmin AD None 21 13 08 Urazole, 16% mole percent... 56 18 38 3-thiourazole, 5 mole percent. 58 l8 40 3,5-dithiourazole, 5 mole percent 61 18 43 3,5-dithiourazole hydrazine salt, 4 mole percent 70 21 49 i-cthylurazole, 15 mole percent. 43 .14 29 l-phenylurazole, 15 mole percent .36 .13 23 4phenylurazole, 15 mole percent 38 13 .25 4-arninourazole hydrazine salt, 5 mole percent- 61 l7 44 3 thio5-iminourazo1e, 4.7 mole percent.. 57 .17 40 As can be observed from the data set out in the table above, light-developable, direct-print silver halide emulsions containing a wide variety of urazole addenda can be utilized to improve the utility of such emulsions. If desired, the exposed coatings can be chemically developed and fixed to form archival quality images, a 1 minute development and a 1.5 minute fix at 72 F. in the following baths being suitable:

DEVELOPING COMPOSITION G. N-Methyl-p-aminophenol sulfate 3.0 Sodium sulfite (anhydrous) 45.0 Hydroquinone 12.0 Sodium carbonate monohydrate 80.0 Potassium bromide 2.0 Sodium thiosulfate 5.0

Benzoxazolethiol 25.0 Water to make 2 liters.

6 FIXING COMPOSITION Sodium thiosulfate ....g 240.0 Sodium sulfite (anhydrous) g 15.0 Acetic acid, 28% cc 48.0 Boric acid g 7.5 Potassium alum g; 15.0 Water to make one liter.

Example 2 A sample of the light-developable, direct-print silver halide emulsion containing 4.7 mole percent of 3-iminothiourazole and coated on a paper support as described in Example 1 was incubated at 120 F. and 35% relative humidity for seven days prior to being exposed and photodeveloped as described in Example 1. The density of the resulting D or image area was .53 and the density of the D or background area was .15, and AD or D D was .38.

Example 3 A light-developable, direct-print silver halide emulsion as described in Example 1 was prepared and coatings were prepared containing 5, 10 and 40 mole percent of urazole based on the silver halide. The coatings contained silver at a coverage of 258 mg. per square foot and gelatin at a coverage of 565 mg. per square foot. Each of the coatings were exposed on an Edgerton, Germeshausen and Grier Mark VII sensitometer containing a xenon flash lamp for 10 microseconds through a 0.15 log E density-increment neutral density step tablet followed by a photodeveloprnent of 5 minutes with a 60 foot-candle cool white fluorescent light. Good image discrimination of the magnitude illustrated by the data set out in Table I above was obtained for each of the coatings after the exposure and photodeveloprnent.

The invention has been described in considerable detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modification scan be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A photographic process for preparing light-developed images which comprises imagewise exposing a lightdevelopable, direct-print silver halide emulsion to a shortduration, high-intensity light of at least about .1 footcandle second at an intensity of more than about foot-candles to form a latent image in said emulsion, and thereafter subjecting the imagewise exposed emulsion to an overall exposure tolight of lower intensity than the said imagewise exposure to photo-develop said latent image, said silver halide emulsion being a light-developable, direct-print silver halide emulsion containing a urazole halogen acceptor having the formula wherein:

(1) X and Z are each selected from the group consisting of an oxygen atom, a sulfur atom, a selenium atom and an imino radical; and

(2) R R and R are each selected from the group consisting of a hydrogen atom, an alkyl radical, an aryl radical and an amino radical, except that at least one of R and R is a hydrogen atom.

2. A light-developable, direct-print, radiation-sensitive silver halide emulsion comprising silver halide grains having a predominant amount of radiation sensitivity internal to said grains and at least about .1 mole percent,

based on said silver halide, of a urazole halogen acceptor having the formula:

R2 c=z wherein:

(1) X and Z are each selected from the group consisting of an oxygen atom, a sulfur atom, a selenium atom and an imino radical; and

(2) R R and R are each selected from the group consisting of a hydrogen atom, an alkyl radical, an aryl radical and an amino radical, except that at least one of R and R is a hydrogen atom.

3. A direct-print emulsion according to claim 16 wherein said emulsion contains from about 1 to about 50 mole percent, based on said silver halide, of said halogen acceptor.

4. A light-developable, direct-print, radiation-sensitive silver halide emulsion comprising silver halide grains having a predominant amount of radiation sensitivity internal to said grains and at least about .1 mole percent, based on said silver halide, of a urazole halogen acceptor having the formula:

limb: H H

wherein R is an alkyl radical.

5. A light-developable, direct-print, radiation-sens1t1ve silver halide emulsion comprising silver halide grains having a predominant amount of radiation sensitivity internal to said grains and at least about .1 mole percent, based on said silver halide, of a urazole halogen acceptor having the formula:

wherein R is an aryl radical.

6. A light-developable, direct-print, radlation-sensitive silver halide emulsion comprising silver halide grainshaving a predominant amount of radiation sensitlvity inter nal to said grains and at least about .1 mole percent, based on said silver halide, of a urazole halogen acceptor having the formula:

wherein R is an amino radical.

wherein R is an aryl radical.

8. A light-developable, direct-print, radiation-sensitive silver halide emulsion comprising silver halide grains having a predominant amount of radiation sensitivity internal to said grains and at least about .1 mole percent, based on said silver halide, of urazole as a halogen acceptor.

9. A light-developable, direct-print silver halide emulsion containing 3,5-dithiou'razole as a halogen acceptor.

10. A direct-print emulsion according to claim 9 where in said halogen acceptor is a hydrazine salt of 3,5-dithiourazole.

11. A direct-print emulsion according to claim 9 containing from about 1 mole percent to about 50 mole percent, based on said silver halide, of said halogen acceptor.

12. A light-developable, direct-print silver halide emulsion containing 3-thiourazole as a halogen acceptor.

13. A light-developable, direct-print silver halide emulsion containing 3-thio-5-iminourazole as a halogen acceptor.

14. A- direct-print emulsion according to claim 8 wherein the halide of said silver halide is predominantly bromide.

15". A direct-print emulsion according to claim 9 wherein the halide of said silver halide is predominantly bromide.

16. A direct-print emulsion according to claim 12 wherein the halide of said silver halide is predominantly bromide.

17. A direct-print emulsion according to claim 13 wherein the halide of said silver halide is predominantly bromide.

-18. A direct-print emulsion according to claim 2 wherein the halide of said silver halide is predominantly bromide.

References Cited UNITED STATES PATENTS 2,534,599 12/1950 Howe 7 2,708,162 5/1955 Carroll et al. 95--7 3,033,682 5/1962 Hunt 96-108 NORMAN G. TORCHIN, Primary Examiner. J. R. EVERE'ITE, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,396 ,017 August 6 1968 Robert E. Bacon et a1.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 15, "discolsed" should read disclosed Column 4, lines 57 and 58, "descrbied" should read described Column 6, lines 39 and 40, "modification scan" should read modifications can Column 7 line 18, "16 should read 2 Signed and sealed this 27th day of January 1970.

(SEAL) Attest: sf Edward M. Fletcher, 11'.

Attesting Officer Commissioner of Patents 

